AB1363 IMAGE PATTERN ANALYSIS IN FLUORESCENCE OPTICAL IMAGING FOR DIFFERENTIAL DIAGNOSIS IN RHEUMATIC JOINT DISEASES
Authors: N. Stumper, J. Berger, G. Schmittat, A. Briel, D. Vogler, G. R. Burmester, P. Hoff, S. Ohrndorf
Journal: Annals of the Rheumatic Diseases (2022)

Background As outlined in previous studies, different rheumatic joint diseases present specific characteristic patterns and features in fluorescence optical imaging (FOI) (1-4). Objectives We tested different features in FOI for their ability to differentiate various rheumatic joint diseases such as rheumatoid arthritis (RA), osteoarthritis (OA) and psoriatic arthritis (PsA) with the aim to identify clear FOI criteria for the diseases. Methods FOI images from patients with RA, OA, PsA and healthy volunteers were evaluated by two readers blinded for diagnosis and calibrated against each other, using the prima vista mode (PVM) and the 5-phase model. For the latter, the overall time course of FOI in each hand was divided into 5 phases with a computational algorithm. Phases 1 and 2 describe the inflow (start to 15% and 15%-90% on rising edge), phase 3 is the peak phase and phases 4 and 5 comprise the outflow (90%-36.8% and 36.8% to end on falling edge). Twenty-six different features were defined by an atlas, for example the streaky pattern feature (T) as a signal enhancement around the PIP area that appears streaky, whereby the stripes are orthogonal to the finger axis (Figure 1a). The cloudy pattern (W) is visible during the inflow on the back of the hand (Figure 1b). The enthesis feature (E) depicts a V shaped and filled pattern between nail and DIP (Figure 1c). The feature frequency in each patient and phase (PVM, 5-phase) was counted and statistically analysed. Figure 1. Examples for FOI patterns and features: a) (T) Streaky pattern in PVM image (OA); b) (W) Cloudy pattern on the back of the hand in phase 1 (PsA); c) (E) Enthesis pattern in phase 3. Results In total, 128 patients (RA (age mean 54.2; SD 10.6; median 52.4), OA (58.0; 14.3; 60.1), and PsA (47.9; 12.7; 46.8)) and healthy volunteers (32 in each group) were included in the feature reading. In our analysis, OA can be differentiated from RA on the basis of the feature T. Feature T is found in phase 3 (χ 2 : 4.61; diagnostic odds ratio (DOR): 7.49; sensitivity (TPR) 0.11; specificity (TNR): 0.98; positive predictive value (PPV): 0.87; negative predictive value (NPV): 0.52), phase 5 (χ 2 : 18.5; DOR: 5.60; TPR 0.55; TNR: 0.82; PPV: 0.76; NPV: 0.64 and PVM (28.3; 12.1; 52%; 92% 87%; 65%). By means of the feature E, a distinction between RA and PsA is only limited possible (χ 2 : 9.58; DOR: 3.65; TPR 0.40; TNR: 0.84; PPV: 0.71; NPV: 0.59). But PsA can well be distinguished from RA by the appearance of pattern W in phase 1 (χ 2 : 7.68; DOR: 6.92; TPR 0.19; TNR: 0.97; PPV: 0.86; NPV: 0.54). Other significant features yield high specificity (70%-98%) while having low sensitivity (12%-52%). Conclusion This work demonstrates that FOI feature analysis has the potential for differential diagnosis with FOI, which could optimize the (early) diagnostic process of rheumatic joint diseases. A majority of features yield high specificity, but only low sensitivity. The combination of different features using artificial intelligence might lead to improved diagnostic accuracy. References [1]Werner SG, et al. Inflammation assessment in patients with arthritis using a novel in vivo fluorescence optical imaging technology. Ann Rheum Dis. 2012; 71(4):504-510. [2]Glimm AM, et al. Analysis of distribution and severity of inflammation in patients with osteoarthitis compared to rheumatoid arthritis by ICG-enhanced fluorescence optical imaging and musculoskeletal ultrasound: a pilot study. Ann Rheum Dis. 2016; 75(3):566-570. [3]Wiemann O, et al. The “green nail” phenomenon in ICG-enhanced fluorescence optical imaging - a potential tool for the differential diagnosis of psoriatic arthritis. J Dtsch Dermatol Ges. 2019;17(2):138-147. [4]Schmidt A, et al. Detection of subclinical skin manifestation in patients with psoriasis and psoriatic arthritis by fluorescence optical imaging. Arthritis Res Ther. 2020; 22(1):192. Disclosure of Interests None declared